The present invention relates to controller-assisted shifting of manually shifted transmissions. In particular, the present invention relates to a control system/method for a manually shifted transmission that, in a preferred embodiment, will (i) sense an operator intent to shift and automatically minimize driveline torque, minimizing torque lock and allowing an easy shift to neutral; and (ii) upon sensing a shift to main section neutral, then sense a target gear ratio, cause the engine to rotate at a substantially synchronous speed for engaging the target ratio, and inhibit/prohibit shifting from neutral until substantially synchronous conditions for engaging the target gear ratio are sensed.
More particularly, the present invention relates to a control system/method for a controller-assisted, manually shifted transmission which will automatically control engine torque and/or speed to allow the vehicle operator to fully engage a target ratio.
Controller-assisted, manually shifted transmission systems are known in the prior art. Typically, such systems include sensors, actuators and a microprocessor-based controller and will automatically assist manual shifting by sensing an operator intent to shift and cause a reduction in driveline torque and/or by sensing an intended target ratio and causing synchronous conditions for engaging the target ratio. Such controller-assisted systems may be seen by reference to U.S. Pats. No. 4,593,580; 4,850,236; 4,676,115; 5,582,558; 5,755,639; 5,735,771; 6,015,366 and published British patent application GB 2,335,010A, the disclosures of which are incorporated herein by reference.
Transmission systems having controls and/or sensors in the shift knobs are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,723,642; 5,228,361 and 5,957,001, the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 5,508,916 illustrates an automated transmission system that will cause dithering about true synchronous during ratio engagement. Allowed, co-pending patent application U.S. Ser. No. 09/330,570 discloses reducing engine output torque upon sensing partial jaw clutch engagement. The disclosures of both of the above are incorporated herein by reference.
The prior art systems were not totally satisfactory, as they required the added cost of providing individual or power synchronizers, they required considerable additional sensors and/or actuators, they required the driver to provide a separate signal of a target ratio, they did not provide a high resistance to shift lever jumpout while still providing high shift quality, they did not minimize shift times, they did not control engine fueling to allow ease of full jaw clutch engagement and/or they did not, with a high degree of reliability, prevent or inhibit non-synchronous shifting.
In accordance with the present invention, the drawbacks of the prior art are minimized or overcome by the provision of a controller-assisted, manually shifted transmission system which will allow easy disengagement of a currently engaged ratio, will inhibit out-of-synchronous shifts and jumpout, and will provide conditions allowing easy, full engagement of jaw clutches associated with a target gear ratio, all with a minimum of added expense, as compared to previously proposed controller-assisted systems.
In the preferred embodiment, the foregoing is accomplished by providing an assist system for a manually shifted transmission, preferably a splitter-type compound transmission driven by an electronically controlled engine communicating with an industry standard electronic data link, such as an SAE J-1939 or J-1922 data link. The system is provided with sensors and logic to sense an intent to shift and the identity of a target ratio and will command automatic engine fueling to reduce driveline torque when disengaging a currently engaged ratio and to synchronize for engaging a target ratio when the transmission is in neutral.
A plunger actuator assembly responds to command signals to selectively extend and retract a detent plunger, which cooperates with grooves on a shift shaft to selectively inhibit Y-Y shift lever movement to inhibit out-of-synchronous ratio engagements and to provide an in-gear detent to resist shift lever whip-induced jumpout.
During engagement of a target ratio, if only partial jaw clutch engagement is sensed from the shift lever position sensors, for a period of time, the engine will be urged to dither about zero driveline torque, which will cause a dither about true synchronous speed, to minimize a torque lock condition, allowing full clutch engagement.
Accordingly, an object of the present invention is to provide a new and improved controller-assisted, manually shifted transmission system.
This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.